feat: cleanup old binary versions after update

[kristinemejia443-netizen]

Summary

• After a successful binary download, delete all previously downloaded version directories from the binary folder, keeping only the current version
• Cleanup also runs automatically on startup for each binary that already has its current version installed
• Errors during cleanup are logged but do not prevent normal operation

Changes

• binaries_manager.rs: Added cleanup_old_versions() method that iterates the binary folder and removes all version subdirectories except the current one. Called after each successful download.
• binaries_resolver.rs: Added cleanup_old_versions() that calls cleanup on all managed binaries. Wired into initialize_binary() so cleanup runs on startup even when no download is needed.

Acceptance Criteria (from #3028)

• After a successful update, all previously downloaded binary versions are deleted from the download directory
• The current (latest, just-installed) binary is always retained
• Cleanup runs automatically on startup or after update completion (no user action required)

Closes #3028

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces a cleanup mechanism for old binary versions within the BinaryManager and BinaryResolver. While the logic correctly identifies and removes unused directories, the feedback highlights several critical improvements: error handling should be 'best-effort' to prevent cleanup failures from interrupting the main download process or batch operations, and synchronous file system calls should be replaced with asynchronous ones to avoid blocking the Tokio runtime.

[gemini-code-assist]

The cleanup process should be "best-effort" for all managed binaries. Using ? inside the loop causes the entire operation to stop if a single binary manager encounters an error during cleanup, preventing subsequent binaries from being processed. This contradicts the goal of not letting cleanup errors prevent normal operation.

        for (binary, manager) in &self.managers {
            let _unused = manager.cleanup_old_versions().await.inspect_err(|e| {
                log::warn!(target: LOG_TARGET_APP_LOGIC, "Failed to cleanup old versions for {}: {e}", binary.name());
            });
        }

References

1. It is acceptable to implement workarounds to prevent errors in fragile downstream components, even if a more robust fix in the component itself is possible.

[gemini-code-assist]

This method uses synchronous I/O (std::fs::read_dir and std::fs::remove_dir_all) inside an async fn. Since cleanup involves iterating over directories and potentially performing recursive deletions of large binary folders, this can block the Tokio worker thread for a significant amount of time. This can lead to performance degradation or UI unresponsiveness in a Tauri application. Consider using tokio::fs for non-blocking file operations.